Early Color Television
Admiral C322C16 Ambassador Restoration
We have two of these sets at the museum. One has a good cabinet, but a bad CRT. The other has a poor cabinet, with a good CRT. We decided to restore the one with the good CRT, since it is attached to the chassis.
We did this restoration using a different approach, since John Folsom was also restoring his Admiral at the same time. I didn't have time to do the normal cleaning of the chassis and complete re-capping. Instead, I left the chassis cleaning for later, and re-capped on a circuit by circuit basis.
First was the power supply and sweep sections. I replaced most of the electrolytics (installed tubular replacements under the chassis) and all the paper capacitors in the sweep sections. The first problem I came up with was that the socket assembly for the 3A3 high voltage rectifier was arcing. I had a similar assembly from an RCA set which I was able to install. After doing this I had about 20 kv on the CRT.
The next problem was that I couldn't get good purity. I discovered that someone had cranked all the rim magnets all the way in. After backing them off, I was able to get decent purity. I did a crude convergence job, and then went on to the video section.
I re-capped the video amplifier sections, and got a decent black and white picture, though it was somewhat blurry, with not very good resolution. Also, I had intermittent flashing in the picture, which I tracked down to a bad IF amplifier tube.
Sync, particularly the horizontal, was very touchy. I replaced a half dozen or so high value resistors that were way off, but that made almost no difference. I then discovered that the dual diode package that serves as the horizontal sync phase detector was bad. After replacing the diode package with a couple of individual general purpose diodes, I had good, stable sync.
I then went on to the color sections. After re-capping these sections, I had very low saturation color, but it wasn't in sync. I spent hours doing the color sync alignment, replacing components and checking voltages and waveforms, with not much luck. Finally, I discovered that the local oscillator in the tuner was off frequency, and that the fine tuning control wouldn't bring it on. Adjusting the channel 3 slug in the tuner brought it on frequency, and solved the poor resolution problem. Also, the color saturation was now right.
Intermittent flashing, this time less severe, came back. I discovered that the problem was bad contact in one or more of the pins of the horizontal output tube. Replacing the metal receptacles in the socket solved that.
AGC was not working properly, and I discovered more bad high value resistors in that circuit, which I replaced.
The color section of this set is particularly hard to troubleshoot because everything has to be working or nothing works. For instance, the color killer is biased by the color phase detector, so problems with that circuit will completely disable the color. Also, having inadequate burst (caused by the local oscillator being off frequency) made color sync alignment impossible.
Now there are two remaining problems. First, the focus pot is bad, though the focus is reaasonably good with the wiper at the extreme (high voltage) end. Second, the horizontal centering is off. I've tried adjusting all the things on the CRT neck, but I can't get the picture centered properly.
I replaced the focus pot and that fixed the centering. The set is now working well.